Front Cover
 Results and discussion

Group Title: Research report - North Florida Experiment Station, University of Florida - 90-2
Title: Toxicity in plants due to copper from pesticides in tomato field soils
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00073718/00001
 Material Information
Title: Toxicity in plants due to copper from pesticides in tomato field soils
Series Title: NFREC, Quincy Research report
Physical Description: 9 leaves : ill. ; 28 cm.
Language: English
Creator: Rhoads, Fred ( Frederick Milton )
Olson, Stephen Michael
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville FL
Publication Date: 1990
Subject: Plants -- Effect of copper on -- Florida   ( lcsh )
Plants -- Effect of pesticides on -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by F.M. Rhoads and S.M. Olson.
General Note: Cover title.
Funding: Research report (North Florida Research and Education Center (Quincy, Fla.)) ;
 Record Information
Bibliographic ID: UF00073718
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 84656244

Table of Contents
    Front Cover
        Page 1
        Page 2
        Page 3
    Results and discussion
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida


NFREC, Quincy Research Report 90-2

Toxicity in Plants Due to Copper



in Tomato



University of Florida
Florida Agricultural Experiren Stations
Institute of Food and Agricultural Sciences
University of Florida, Gainesville




CI=lrar I


Copper containing pesticides are used in North Florida tomato

fields to control diseases that reduce yield and quality of the

local staked tomato crop. As much as 30 lb copper acre"1 may be

applied annually in cases of severe disease outbreak. Research

results show that once copper gets into the soil it moves very

little and tends to accumulate in the plow layer.

Symptoms of copper toxicity in commercial tomato crops in

North Florida have not been reported. However, symptoms of

suspected copper toxicity in oats following tomatoes were observed

in the fall of 1989. The literature does not contain extensive

information on copper toxicity in plants. Therefore, specific

symptoms of copper toxicity in tomatoes and oats were not found in

the literature. However, corn was reported to have reduced growth,

chlorosis of foliage, and stunted root development as a result of

copper toxicity. Tomatoes grown in pots of soil containing high

levels of copper exhibited reduced growth inversely proportional to

soil-copper content. Oats growing in a tomato field in the fall of

1989 exhibited severe foliage chlorosis where soil-copper level was

near 200 lb acre"1.

This report summarizes the results of a greenhouse experiment

with tomatoes growing in pots of soil containing varying amounts of

copper. In addition, soil-test and tissue-test results from a

field of oats following tomatoes and a field of oats where tomatoes

have not been grown are reported.


Two greenhouse experiments were conducted to determine the

effect of high soil-copper levels on the growth of tomato plants.

Tomato seedlings ('Sunny') were grown for six weeks in one-half

gallon pots of topsoil similar to that in most commercial tomato

fields. Copper hydroxide was added to the soil in experiment-i in

amounts ranging from zero to 5600 lb of copper acre"'. Calcite

(CaCO3) was added at rates of zero and 3.5 tons acre"' for each

level of copper in experiment-1. Rates of copper (as copper

hydroxide) in experiment-2 ranged from 0 to 1400 lb acre"' with lime

(CaCO3) levels at 0 and 7.0 tons acre"'. Each experiment contained

six rates of copper and two rates of lime for a total of 12

treatments with six replicates. Nutrient solutions containing

uniform levels of N, P, and K were added to each experiment to

maintain rapid growth.

At the end of a six-week growth period plant tops (cut at soil

surface) were harvested, dried, weighed, and analyzed for copper

content. Soil samples were collected from each pot after harvest

and Mehlich-I (extractant used in Florida extension soil testing

lab) soil copper and soil pH were determined.

Severe foliage chlorosis was observed in oats following

tomatoes in the fall of 1989. Soil samples were taken at two

depths (0-6 in and 6-12 in) at two locations (no symptoms and

severe symptoms) in the oats following tomatoes and in a field of

oats where tomatoes have not been grown. In addition, foliage

samples were taken at the same locations as the soil samples. Soil

and plant samples were analyzed for copper content and plant

samples were analyzed for nitrogen content.



High copper rates reduced growth of tomatoes in experiment-i

without other visible symptoms (Fig. 1). Lime increased growth of

tomatoes at 350 and 700 lb of copper acre"'. However, lime did not

influence growth with the 1400 lb acre"' copper rate. Soil pH

ranged from 4.8 to 5.5 with no lime and from 5.9 to 6.5 with lime.

Data in Figure 2 are a combination of results from experiment-

1 and experiment-2. Liming to pH 6.5 neutralized the effect of

copper on growth of tomatoes at soil-copper rates less than 701 lb

acre-1. Growth of tomatoes was reduced more than 40% with a soil-

copper rate of 1400 lb acre"' at soil-pH levels between 6.5 and 7.2.

This suggests that lime cannot neutralize the effect of extremely

high levels of copper in the soil. The level of soil copper could

possibly surpass 1400 lb acre"' after 50 years of continuous tomato

production with annual applications of 30 Ib of copper acre"1.

Therefore, continued high rates of copper-containing pesticides

could create serious problems for future generations in the form of

copper-contaminated soils.

Copper rates greater than 200 lb acre"1 produced maximum copper

concentration in tomato tissue (Fig. 3). A positive linear

response occurred between 0 and 208 lb copper acre"' and a linear

plateau response occurred above 208 lb copper acre"1. Tissue copper

was greater than 30 ppm in all cases of reduced growth due to








Cu Rate (Ib/acre)
Figure 1. Growth of tomato plants as a function of copper and lime rates.

Yield (g/plant)

0 Lime

3.5 tons/acre




M 700 Ib Cu/A lP 1400 Ib Cu/A

Relative Yield (%)

5.3 6.3 6.6 7.4 4.8 6.5 6.6 7.4 4.8 6.3 6.5 7.3 5.3 6.3 6.6 7.1
Soil pH
Figure 2. Growth of tomato plants as a function of copper rate and soil pH.








= 350 Ib Cu/A

M 0 Cu

Copper in

Tissue (ppm)





A 0 Lime
Exp. 13.5 tons/acre
^g 3.5 tons/acre

r = 0.77

Exp. 2<

7.0 tons/acre

200 400 600 800 1000
Cu Rate (Ib/acre)
Copper concentration in tomato plant tissue




as a function of copper

Y = 12.8 +0.104X, if X < 208
Y = 34.3, if X = or > 208

0 Lime

Figure 3.

copper toxicity but, plant growth was not reduced in all cases with

tissue copper greater than 30 ppm. Therefore, tissue copper level

is not a reliable index of copper toxicity.


Copper concentration in oat tissue was positively correlated

with extractable soil copper in the 0 to 6" soil layer (Table 1.).

The lowest copper concentration in oats (11 ppm) occurred with 3 lb

copper acre"' in the 0 to 6" soil layer. Oats with severe chlorosis

contained 32 ppm copper while growing in soil containing 192 Ib

copper acre"1. Plants with 18 ppm copper showed no toxicity

symptoms. Toxicity occurred in oats with a tissue level of copper

similar to that of tomatoes with reduced growth due to excessive

copper. Oats showing symptoms of toxicity were lower in nitrogen

but were not in the deficient range. This suggests that chlorosis

was not due to nitrogen deficiency.

Table 1. Copper and'nitrogen content of oat tissue and copper
content of soil samples from two fields.

Sample Oat Tissue Soil
Field area Cu N 0-6" 6-12"

ppm % -lb Cu/acre-

Oats (1) No symptoms 11 4.38 3 2

Tomato (2) No symptoms 18 4.30 56 -

Tomato (2) Severe symptoms 32 3.80 192 5

ii --

Extractable soil copper (sample from tomato field with

chlorotic oats) in the 0 to 6" layer was 192 lb acre'1 while the 6

to 12" layer beneath contained only 5 lb acre"'. When compared with

soil samples from a field where tomatoes have not been grown, this

represents a 64-fold increase in copper content for the 0 to 6"

layer and 2 1/2 fold increase for the 6 to 12" layer. Obviously,

copper is relatively immobile in the soil.

Ways to Reduce the Potential for Copper Toxicity

in Tomato Fields

1 Lime the soil to pH of 6.5 to 7.0. The

extension soil testing lab (University of

Florida) can determine lime requirement from a

soil sample for a specific soil pH.

2 Grow disease resistant varieties to reduce the

need for copper containing pesticides.

3 Rotate tomato crops between fields.

4 Deep plow to dilute the accumulated copper in

the 0-6" plow layer.

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